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Strathprints serves world leading Open Access research by the University of Strathclyde, including research by the Strathclyde Institute of Pharmacy and Biomedical Sciences (SIPBS), where research centres such as the Industrial Biotechnology Innovation Centre (IBioIC), the Cancer Research UK Formulation Unit, SeaBioTech and the Centre for Biophotonics are based.

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Diode laser spectroscopy using a calibration free phasor decomposition approach with RAM nulling

Ruxton, K.C. and Chakraborty, A. and McGettrick, A.J. and Duffin, K. and Johnstone, W. and Stewart, G. (2009) Diode laser spectroscopy using a calibration free phasor decomposition approach with RAM nulling. In: 7th International Conference on Tunable Diode Laser Spectroscopy, 2009-07-13 - 2009-07-17.

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Abstract

A limiting factor of tunable diode laser spectroscopy (TDLS) analysis is the large unwanted residual amplitude modulation (RAM) background present on the recovered 1st harmonic signal. A novel approach to remove the background RAM will be presented. This new technique will be used alongside the phasor decomposition method (PDM) [1], a calibration free technique for recovery of the absolute gas absorption line-shape. The RAM nulling method developed, successfully removes the background by optical cancellation. This is achieved by placing a fibre delay line, which introduces a π phase change in the modulation signal, in parallel with the gas cell line. When these lines are coupled together the background signals are at anti-phase and hence cancel each other. The main benefit being that measurement sensitivity can be increased. Results illustrating RAM nulling whilst using the PDM technique for absorption line-shape recovery will be presented. Figure 1 shows a recorded PDM measurement illustrating the difference with and without RAM Nulling.